| From 9cb63711e63042f22da914ba039c4537b22e8fb0 Mon Sep 17 00:00:00 2001 |
| From: Greg Hudson <ghudson@mit.edu> |
| Date: Fri, 25 Sep 2015 12:51:47 -0400 |
| Subject: [PATCH 3/4] Fix build_principal memory bug [CVE-2015-2697] |
| |
| In build_principal_va(), use k5memdup0() instead of strdup() to make a |
| copy of the realm, to ensure that we allocate the correct number of |
| bytes and do not read past the end of the input string. This bug |
| affects krb5_build_principal(), krb5_build_principal_va(), and |
| krb5_build_principal_alloc_va(). krb5_build_principal_ext() is not |
| affected. |
| |
| CVE-2015-2697: |
| |
| In MIT krb5 1.7 and later, an authenticated attacker may be able to |
| cause a KDC to crash using a TGS request with a large realm field |
| beginning with a null byte. If the KDC attempts to find a referral to |
| answer the request, it constructs a principal name for lookup using |
| krb5_build_principal() with the requested realm. Due to a bug in this |
| function, the null byte causes only one byte be allocated for the |
| realm field of the constructed principal, far less than its length. |
| Subsequent operations on the lookup principal may cause a read beyond |
| the end of the mapped memory region, causing the KDC process to crash. |
| |
| CVSSv2: AV:N/AC:L/Au:S/C:N/I:N/A:C/E:POC/RL:OF/RC:C |
| |
| ticket: 8252 (new) |
| target_version: 1.14 |
| tags: pullup |
| |
| Backport upstream commit: |
| https://github.com/krb5/krb5/commit/f0c094a1b745d91ef2f9a4eae2149aac026a5789 |
| |
| Upstream-Status: Backport |
| --- |
| src/lib/krb5/krb/bld_princ.c | 6 ++---- |
| 1 file changed, 2 insertions(+), 4 deletions(-) |
| |
| diff --git a/src/lib/krb5/krb/bld_princ.c b/src/lib/krb5/krb/bld_princ.c |
| index ab6fed8..8604268 100644 |
| --- a/src/lib/krb5/krb/bld_princ.c |
| +++ b/src/lib/krb5/krb/bld_princ.c |
| @@ -40,10 +40,8 @@ build_principal_va(krb5_context context, krb5_principal princ, |
| data = malloc(size * sizeof(krb5_data)); |
| if (!data) { retval = ENOMEM; } |
| |
| - if (!retval) { |
| - r = strdup(realm); |
| - if (!r) { retval = ENOMEM; } |
| - } |
| + if (!retval) |
| + r = k5memdup0(realm, rlen, &retval); |
| |
| while (!retval && (component = va_arg(ap, char *))) { |
| if (count == size) { |
| -- |
| 1.9.1 |
| |